1. Field of the Invention
The present invention relates to an apparatus and method for managing a defect caused by scratches on a hard disk, and more particularly, to a hard disk drive defect-free algorithm which makes it possible to record user data on normal sectors rather than defective sectors by putting alleged defects on a defect list.
2. Description of the Related Art
FIG. 1 is a diagram illustrating a first operation of a method of managing vertical scratches using a conventional algorithm. Referring to FIG. 1, let us assume that information indicating that an n-th track has a defective sector is read from a defect list (11). Then, the next ten vertically adjacent tracks, ranging from the n-th track to an n+9-th track, are checked for a defective sector. As shown in FIG. 1, the n+8-th track also has a defective sector. Because there is another track having a defective sector other than the n-th track among the ten vertically adjacent sectors, sectors of the ten vertically adjacent tracks are all set as alleged defective sectors and then treated as a scratch.
Alternatively, supposing that information that an n-th track has a defective sector is drawn from a defect list (12), then ten vertically adjacent tracks, ranging from the n-th track to an n+9-th track, are checked for a defective sector. As shown in FIG. 1, if there is more than one track having a defective sector among the ten vertically adjacent tracks, a defective sector of the track that is farthest away from the n-th track among those having a defective sector is set as a target sector. In FIG. 1, a defective sector of an n+8-th track could be the target sector. Thereafter, all sectors of the ten vertically adjacent tracks from the n-th track to the n+9-th track are set as alleged defective sectors and then treated as a scratch.
FIG. 2 is a diagram illustrating a second operation of the method of managing a vertical scratch using the conventional algorithm. After the first operation of FIG. 1, lower tracks of the n-th track are checked for a defective sector. For example, if there is a track having a defective sector among 24 lower tracks of the n-th track, all sectors between the defective track of the corresponding track and the defective sector of the n-th track are set as alleged defective sectors and then treated as including a scratch. Likewise, upper tracks of the n-th track are checked for a defective sector. For example, if there is a track having a defective sector among 24 upper tracks of the n-th track, all sectors between the defective track of the corresponding track and the defective sector of the n-th track are set as alleged defective sectors and then treated as a scratch.
FIG. 3 is a diagram illustrating a third operation of the method of managing a vertical scratch using the conventional algorithm. As shown in FIG. 3, if there are defective sectors between an n−20-th track and an n+28-th track, all sectors therebetween are set as alleged defective sectors and then treated as a scratch. More specifically, the size of a scratch is calculated using the following equation: size=(defect length)/8+5. Thereafter, as large an area of a hard disk as the calculation result is treated as a scratch. For example, in the case of the tracks of FIG. 3, the calculated size of a scratch amounts to (49/8+5). Therefore, as many lower tracks of the n−20-th track as (49/8+5) and as many upper tracks of the n+28-th track as (49/8+5) are additionally treated as a scratch.
As a part of a device, a hard disk seldom includes scratches on the surface until it is assembled into a device along with other parts. However, since a hard disk and a head/disk assembly (HAD) are jig-assembled by moving a head along a pivot of the hard disk with the hard disk at a standstill, an arc-shaped scratch can be formed along the trajectory of the head. The arc-shaped scratch can be seen as being perpendicular to a track direction of the hard disk from a microscopic point of view. Conventionally, scratch filling has been generally performed in expectation of only vertical scratches.
Nowadays, however, hard disk drives are manufactured to be capable of rotating at higher revolutions-per-minute (RPM) and to have higher track-per-inch (TPI) and higher bits-per-inch (BPI) as a result of increasing storage capacities. Accordingly, it becomes more likely that scratches will be more easily formed on the surface of hard disks in random directions, particularly, in a slant-line direction or a horizontal direction with respect to the track direction of the hard disks, because of physical impact on the hard disks or because of a head moving back and forth over a hard disk while the hard disk rotates. However, conventional vertical scratch filling is not efficient enough to treat such random-directional scratches, and thus a brand-new technique of managing random-directional scratches on a hard disk is necessary.